Wireless mobile communication technology uses various standards and protocols to transmit data between a node (e.g., a transmission station) and a wireless device (e.g., a mobile device). Some wireless devices communicate using orthogonal frequency-division multiple access (OFDMA) in a downlink (DL) transmission and single carrier frequency division multiple access (SC-FDMA) in an uplink (UL) transmission. Standards and protocols that use orthogonal frequency-division multiplexing (OFDM) for signal transmission include the third generation partnership project (3GPP) long term evolution (LTE), the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard (e.g., 802.16e, 802.16m), which is commonly known to industry groups as WiMAX (Worldwide interoperability for Microwave Access), and the IEEE 802.11 standard, which is commonly known to industry groups as WiFi. In 3GPP radio access network (RAN) LTE systems, the node can be a combination of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs) and Radio Network Controllers (RNCs), which communicate with the wireless device, known as a user equipment (UE). The downlink (DL) transmission can be a communication from the node (e.g., eNodeB) to the wireless device (e.g., UE), and the uplink (UL) transmission can be a communication from the wireless device to the node.
In addition, in wireless communication systems, it is common that a single base station transmits signals to a plurality of remote units. In order to combat the harsh multipath wireless transmission channel while providing signaling to a plurality of remote units, modulation and coding schemes, which provide efficient data transfer, as well as user channelization, have been developed. In general, these schemes operate most efficiently when each signal from a base station is transmitted with synchronized timing. For example, in a typical overlaid code division multiple access (CDMA) system, the signals are distinguished from one another through the use of different codes. In the case of transmissions from a base station to a remote unit, these codes are typically an orthogonal set of codes such as, for example, Walsh functions. If the transmissions corresponding to one orthogonal channel become misaligned with the transmissions corresponding to another channel, the orthogonal nature of the codes is degraded and the transmissions may significantly interfere with one another.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the application is thereby intended.